A preferred non-surgical method for inserting a catheter involves the use of the Seldinger technique which includes an access needle that is inserted into the patient's vein. A guidewire is then inserted through the needle and into the vein. The needle is then removed and a dilator and sheath combination are then inserted over the guidewire. The dilator and sheath combination are then inserted a short distance into the tissue to dilate the incision and the dilator is then removed and discarded. The catheter is then inserted through the sheath into the vein in the desired location.
In a device to introduce a catheter into a blood vessel such as for angiography, hemodialysis or other vascular access procedures, a catheter introducer is used. As shown in FIG. 1, symbol 1 denotes a catheter introducer in general. The catheter introducer 1 includes a sheath member 2, a dilator member 3, a sheath hub 4, a sheath portion 5, a female hole 6, a dilator hub 7, a dilator portion 8, a male prism 9, and an optional side tube 10.
As can be seen in the drawing, the prior art catheter introducer 1 of FIG. 1 is composed of the sheath member 2 consisting of the sheath portion 5 and the sheath hub 4 and the dilator member 3 which consists of the dilator portion 8 and the dilator hub 7. The catheter introducer 1 has the dilator member 3 positioned in the sheath member 2, and is inserted into a blood vessel over a guide wire in the manner briefly described above.
FIGS. 2 and 3 are illustrations showing how the prior art catheter introducer of FIG. 1 may be used. In the drawings, symbol 11 denotes an optional three-way stop cock, a guide wire is designated by symbol 12, subcutaneous tissue is designated by symbol 13, and symbol 14 designates a blood vessel. When the catheter introducer 1 is used, a hollow needle (not illustrated) with an inner needle inserted through it is introduced into the blood vessel 14, and after removing the inner needle, the guide wire 12 is inserted through the hollow needle. The hollow needle is subsequently removed, to leave only the guide wire 12 in the blood vessel. Then, as shown in FIG. 2, the catheter introducer 1 with the dilator member 3 inserted in the sheath member 2 is inserted into the blood vessel 14 with the guide wire 12 operating as a guide. The catheter introducer 1 is introduced until the sheath portion 5 of the sheath member 2 is at least partially inserted into the blood vessel 14. As shown in FIG. 3, the dilator member 3 and the guide wire 12 may be subsequently removed. Then, a catheter is inserted into the sheath member 2 which operates to guide the tip of the catheter through the incision and into the blood vessel 14 to complete the insertion of the catheter. Subsequently, as desired, the three-way stop cock 11 may be actuated to supply a medicine, etc. into the blood vessel through the sheath member 2 or the sheath portion 5 of the sheath member 2 may be split or torn into two sections as the sheath member 2 is removed from around the catheter as described below.
During insertion of the catheter introducer 1 into the blood vessel 14, the sheath member 2 is typically held near the surface of the skin of the patient and gently twisted as the catheter introducer 1 is inserted through the subcutaneous tissue and into the vein of the patient. However, to achieve this, a mechanism for mutually arresting the movement of the dilator member 3 and the sheath member 2 is desired to prevent the relative rotation between the dilator member 3 and the sheath member 2 as well as to prevent the longitudinal displacement of the dilator member 3 relative to the sheath member 2.
To prevent the relative rotation and longitudinal displacement of the dilator member 3 with respect to the sheath member 2, several prior art devices have been disclosed. For example, the device as shown in FIG. 1 is disclosed in PCT Application No. US93/00437 and includes a female polygonal hole 6 formed in the sheath member 2 and a male prism 9 formed in the dilator member 3. The male prism 9 of the dilator member 3 is inserted in the female hole 6 of the sheath member 2 to prevent the relative rotation between the dilator member 3 and the sheath member 2. Furthermore, the female polygonal hole 6 has a groove 6a formed and the male prism 9 has a rib 9a formed so that when the male prism 9 of the dilator member 3 is inserted in the female polygonal hole 6 of the sheath member, the rib 9a of the male prism 9 is fitted in the groove 6a of the female polygonal hole 6 to resist the axial displacement of the dilator member 3 and the sheath member 2.
FIG. 4 shows a further prior art device disclosed in the PCT patent application. The male engaging part 15 of the dilator member 3 and the female engaging part 16 of the sheath member 2 are tapered and hexagonal in cross section. The tapered engagement between the dilator member 3 and the sheath member 2 can prevent the axial displacement and the relative rotation between the sheath member 2 and the dilator member 3.
The prior art device shown in FIGS. 5 and 6 is also disclosed in the PCT patent application. FIG. 5 is a front view showing the end of the sheath member 2 with a female taper portion 17 with recesses 18 and FIG. 6 is a side view showing the dilator member 3 with a male taper portion 19 with protrusions 20. The male taper portion 19 of the dilator member is inserted into the female taper portion 17 of the sheath member to prevent the axial displacement by the taper portion 17, and to prevent the relative rotation by the engagement between the protrusions 20 and the recesses 18.
The prior art device shown in FIG. 7 is also shown in the PCT patent application. In this device, a spiral protrusion 21 is formed around the end 2a of the sheath member and a recess 22 to be engaged with the protrusion 21 of the sheath member is formed on the end 3a of the dilator hub 7 for fastening the dilator member 3 and the sheath member 2 together.
Finally, an example of a further prior art catheter introducer device is shown in FIG. 8. This prior art device is assigned to the Assignee of the present invention and is more fully shown in Design U.S. Pat. No. 318,733. This type of catheter introducer device includes a pull apart sheath and may be used with oval or round catheters and dilators.